Nicholas Piël wrote a great blog introducing readers to the basic concepts of ZeroMQ.

ZeroMQ is a messaging library, which allows you to design a complex communication system without much effort. It has been wrestling with how to effectively describe itself in the recent years. In the beginning it was introduced as ‘messaging middleware’ later they moved to ‘TCP on steroids’ and right now it is a ‘new layer on the networking stack’.

I had some trouble understanding ZeroMQ at first and really had to reset my brain. First of all, it is not a complete messaging system such as RabbitMQ or ActiveMQ. I know the guys of Linden Research compared them, but it is apples and oranges. A full flexed messaging system gives you an out of the box experience. Unwrap it, configure it, start it up and you’re good to go.

ZeroMQ is not such a system at all; it is a messaging library to be used programmatically. It basically gives you a pimped socket interface allowing you to quickly build your own messaging system.